1. Field of the Invention
The present invention relates to a mold for slip casting to obtain a compact by means of casting slip.
2. Description of the Prior Arts
The method for slip casting is roughly classified into two, depending on the way of solidifying slip. One method uses a mold having a feature of absorbing liquid and comprising gypsum ,or porous resin, wherein a part of liquid content in the slip which is cast into this mold is absorbed in the mold to give a feature of maintaining a shape to the slip and then to form a compact by disassembling the mold. Another one uses a mold having a feature of not absorbing liquid and comprising metal, rubber or the like. In this method, the mold is cooled down to the melting point temperature of the liquid contained in the slip or less in advance to cast the slip into the mold, or the slip is firstly cast into the mold at room temperature and thereafter the mold is cooled down to the melting point temperature of the liquid or less, and then, the liquid is solidified to give the feature of maintaining a shape to the slip. The compact is thus prepared by disassembling the mold.
According to those methods mentioned above, when a hollow compact having a complicated inside shape, i.e. one requiring a core being too complicated and hard in shape to be drawn out of the mold because the slope is open toward the inside, the core has to be given a drawing slope so as to make it easy to draw out the core. For this reason, contrivance such as making a core composed of divisible parts is adopted. But, some drawbacks take place, for example, a hollow shape of the core has to be limited, or assembling of the divisible parts becomes difficult. Another method is considered, wherein a core is made of gypsum, and the core is broken after the completion of a compact, but the compact is easy to crack or chip during the work of breaking the core.
Furthermore, in a Japanese Patent Application Laid Open No. 190811/84 a method of using a gypsum mold containing an organic matter insoluble in water by making use of water as a dispersion medium, is disclosed. This mold features lowering its own strength by absorption of moisture to break down of itself, and resultantly this method facilitates the work of demolding the mold. In this point, this method has an effect, in particular, on application to a mold having a complicated shape. The biggest disadvantage of this method is that this mold cannot be applied to metal powders and non-oxide ceramic powders having no affinity to water, and the coverage of the usage is so limited.